Nato poised to strike as Serb general remains defiant

The United Nations and Nato last night began considering a resumption of air strikes against Bosnian Serbs after a 2100 GMT ultimatum to lift the siege of Sarajevo passed.

UN sources in Zagreb said blasts heard in the Bosnian Serb stronghold of Pale were not the result of air strikes. The United Nations earlier said a response by the Bosnian Serb army commander, General Ratko Mladic, to UN and Nato demands to withdraw heavy weapons from around Sarajevo was unacceptable.

"It does not meet our demands," the UN spokesman in Zagreb, Chris Gunness, said. "Serious consideration is now being given to a resumption of air strikes." Gen Mladic, had refused to comply with UN demands to pull back weapons and open roads into the city except on conditions already deemed unacceptable by Nato. But an hour after the 11pm deadline, the UN received reports that the Serbs were assembling weapons in the suburbs of Ilidza, Hadzici, Lukavica, Grbavica and Vogosca. "They are highly unusual movements, so it appears the weapons are ready for withdrawal," a UN spokesman said, adding that officials were not yet sure whether the guns had begun to roll out of the 20km exclusion zone. "That's what we have to clarify."

Mr Gunness said the UN and Nato were assessing the reports and deciding whether to order fresh air strikes. "We believe there are weapons being taken to three points, but whether that is good enough remains to be seen. The assessment continues."

The UN had given General Ratko Mladic untill 11pm to start pulling back the guns targeting the city or face massive Nato retaliation, but despite promises of compliance from political leaders, Gen Mladic was defiant. In a letter faxed to General Bernard Janvier, the UN force commander, Gen Mladic refused international demands. As a military commander, he said, he could not take a decision that might jeopardise Serbs living near Sarajevo: the matter would go to the Bosnian Serb "parliament" and, maybe, a referendum.

On Sunday, Gen Janvier reiterated the conditions under which Nato would end its bombing campaign, following an earlier rejection of his demands by Gen Mladic.

"You must begin withdrawal of heavy weapons from the 20km exclusion zone around Sarajevo before 2300 hours, 4 September 1995," Gen Janvier wrote to the Serb commander. He ordered Serb forces to end all attacks on Sarajevo and three other UN-declared "safe areas" and to guarantee absolute freedom of movement to peace-keepers and aid workers.

The latter demand included the re-opening of Sarajevo's airport which has been closed since April by Serb threats against aid planes.